ENVS10001 Lecture Notes - Lecture 3: Calcium Sulfate, Silicon Dioxide, Mafic
17 May 2018
School
Department
Course
Professor
ROCKS + MINERALS PRACTICAL
Minerals
Primary Minerals: found in igneous rocks + formed as a result
of cooling + differentiation of molten silicate materials (magma)
• Categorised as either mafic or felsic
• Mafic: silicates which contain iron + magnesium, + dark in
colour
• Felsic: silicates with combinations of calcium, sodium, potassium + aluminum, + generally pale
in colour (except quartz = pure silicon dioxide)
Secondary Minerals: products of weathering of primary minerals, + one of main parts of soil
• If deposited + solidified into rocks (lithifed) ! product is sedimentary rock
• Simple salts (sodium chloride, calcium carbonate + calcium sulphate)
• New stable silicates (clays)
• Oxides (predominantly of iron + aluminum)
Mineral
Structure
Mineral Type + Colour
Hardness
Cleavage type or Fracture
Quartz
Framework
Felsic + White
7
Fracture irregular
Biotite
Sheet
Mafic + Black
< 2.5
Cleavage in 1 direction
Feldspar
Framework
Felsic + Pinky-grey
7 > 5.5
Cleavage in 2 directions at 90°
Parent Rock
Metamorp
hic Rock
Metamorphic
Grade
Sandstone
Quartzite
Low to high
Limestone
Marble
Low to high
Granite
Schist
Moderate
Gneiss
High
Shale
Slate
Low
Schist
Moderate
Gneiss
High
Rock
Granite
Basalt
Type
Igneous Intrusive
(Plutonic)
Igneous Extrusive
(Volcanic)
Crystals
Medium to coarse-
grained crystals
(Phaneritic)
Very fine-grained
crystals (Aphanitic)
Mineral
Type
Light + dark minerals –
Felsic, some mafic
Dark minerals -
Mafic
Minerals
Quartz, Feldspar +
Biotite
Olivine +
Pyroxene
Uses
similar
Landscaping boulders, fill for construction
+ building
Uses
different
Monuments +
benchtops
Stone walls + kerb
stones
Minerals: naturally occurring
inorganic chemical compounds
with specific internal structure +
chemical composition
Rocks: natural mixtures or
aggregates of minerals
Characteristics of Rock-Forming Minerals
•Minerals are differentiated by examining properties: streak, colour, hardness +
cleavage/fracture
•Colour: tested by streak colour ! scrape mineral sample on unglazed ceramic tile
•Hardness: tested using Moh’s scale, 1 (soft) ! 10 (hard)
•Cleavage + Fracture: describes way mineral breaks
oCleavage: occurs when mineral breaks along a plane (flat) surface
oFracture: if doesn’t break along plane, then mineral is said to fracture ! smooth,
irregular or conchoidal
Document Summary
Primary minerals: found in igneous rocks + formed as a result of cooling + differentiation of molten silicate materials (magma: categorised as either mafic or felsic, mafic: silicates which contain iron + magnesium, + dark in colour. Minerals: naturally occurring inorganic chemical compounds with specific internal structure + chemical composition. Rocks: natural mixtures or aggregates of minerals: felsic: silicates with combinations of calcium, sodium, potassium + aluminum, + generally pale in colour (except quartz = pure silicon dioxide) If deposited + solidified into rocks (lithifed) ! product is sedimentary rock. Characteristics of rock-forming minerals cleavage/fracture: colour: tested by streak colour ! scrape mineral sample on unglazed ceramic tile, hardness: tested using moh"s scale, 1 (soft) ! 10 (hard: cleavage + fracture: describes way mineral breaks, cleavage: occurs when mineral breaks along a plane (flat) surface, fracture: if doesn"t break along plane, then mineral is said to fracture ! smooth, irregular or conchoidal.
